Fuel system having a cooled injector

ABSTRACT

A fuel system for an engine is disclosed. The fuel system may have a gaseous fuel injector configured to inject gaseous fuel radially into a cylinder of the engine. The fuel system may also have a primary cooling line configured to circulate coolant through the engine. The fuel system may also have an auxiliary cooling line fluidly connecting the primary cooling line with the gaseous fuel injector.

TECHNICAL FIELD

The present disclosure is directed to a fuel system and, moreparticularly, to a fuel system having a cooled injector.

BACKGROUND

Due to the rising cost of liquid fuel (e.g. diesel fuel) and everincreasing restrictions on exhaust emissions, engine manufacturers havedeveloped dual-fuel engines. An exemplary dual-fuel engine providesinjections of a low-cost gaseous fuel (e.g. natural gas) through airintake ports of the engine's cylinders. The gaseous fuel is introducedwith clean air that enters through the intake ports and is ignited byliquid fuel that is injected during each combustion cycle. Because alower-cost fuel is used together with liquid fuel, cost efficiency maybe improved. In addition, the combustion of the gaseous and liquid fuelmixture may result in a reduction of harmful emissions.

Engine parts near the cylinders may be exposed to high temperaturesassociated with fuel combustion. For example, in a dual-fuel engineutilizing gaseous fuel injectors at each cylinder's air intake ports,the efficiency and integrity of these injectors may be materiallyaffected by the extreme temperatures. Various cooling systems have beendeveloped to cool injectors to workable temperatures and to achievedesirable efficiency and part lifetime.

An exemplary arrangement for cooling a liquid injector is disclosed inU.S. Pat. No. 7,021,558 that issued to Chenanda et al. on Apr. 4, 2006.In particular, the '558 patent discloses a liquid fuel injector having acooled lower nozzle body. The liquid fuel injector includes anadditional fuel passage in the lower nozzle body that receives a meteredamount of fuel. This additional passage provides greater surface areaover which fuel can flow. The additional surface area improves coolingof the liquid fuel injector by exposing more of the lower nozzle body tothe relatively low-temperature fuel.

Although the design in the '558 patent may improve cooling of a liquidfuel injector, its applicability may be limited. For instance, the useof a single cooling passage may limit the cooling effect. In addition,other parts of the injector, such as electrical components, may not besufficiently cooled by the additional passage inside the lower nozzlebody. Further, the additional passage may not be practical for gaseousfuel injectors that typically require larger nozzles with fewerrestrictions.

The disclosed fuel system is directed to overcoming one or more of theproblems set forth above and/or other problems of the prior art.

SUMMARY

In one aspect, the present disclosure is directed to a fuel system foran engine. The fuel system may include a gaseous fuel injectorconfigured to inject gaseous fuel radially into a cylinder of theengine. The fuel system may also include a primary cooling lineconfigured to circulate coolant through the engine. The fuel system mayalso include an auxiliary cooling line fluidly connecting the primarycooling line with the gaseous fuel injector.

In another aspect, the present disclosure is directed to a method ofcooling a fuel injector of an engine. The method may include circulatinga coolant via a primary cooling line located in an air box of theengine. The method may also include directing the coolant through anauxiliary cooling line to a gaseous fuel injector to cool the gaseousfuel injector. The method may additionally include returning the coolantto the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional illustration of a dual-fuel engine equippedwith an exemplary disclosed fuel system; and

FIG. 2 is a cross-sectional illustration of the dual-fuel engineequipped with another exemplary disclosed fuel system.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary internal combustion engine 10. Engine 10is depicted and described as a two-stroke dual-fuel engine. Engine 10may include an engine block 12 that at least partially defines aplurality of cylinders 16 (only one shown), each having an associatedcylinder head 20. A cylinder liner 18 may be disposed within each enginecylinder 16, and cylinder head 20 may close off an end of liner 18. Apiston 24 may be slidably disposed within each cylinder liner 18. Eachcylinder liner 18, cylinder head 20, and piston 24 may together define acombustion chamber 22 that receives fuel from a fuel system 14 mountedto engine 10. It is contemplated that engine 10 may include any numberof engine cylinders 16 with corresponding combustion chambers 22.

Within engine cylinder liner 18, piston 24 may be configured toreciprocate between a bottom-dead-center (BDC) or lower-most position,and a top-dead-center (TDC) or upper-most position. In particular,piston 24 may be an assembly that includes a piston crown 26 pivotallyconnected to a rod 28, which may in turn be pivotally connected to acrankshaft 30. Crankshaft 30 of engine 10 may be rotatably disposedwithin engine block 12 and each piston 24 coupled to crankshaft 30 byrod 28 so that a sliding motion of each piston 24 within liner 18results in a rotation of crankshaft 30. Similarly, a rotation ofcrankshaft 30 may result in a sliding motion of piston 24. As crankshaft30 rotates through about 180 degrees, piston crown 26 and connected rod28 may move through one full stroke between BDC and TDC. Engine 10,being a two-stroke engine, may have a complete cycle that includes apower/exhaust/intake stroke (TDC to BDC) and an intake/compressionstroke (BDC to TDC).

During a final phase of the power/exhaust/intake stroke described above,air may be drawn into combustion chamber 22 via one or more gas exchangeports (e.g., air intake ports) 32 located within a sidewall of cylinderliner 18. In particular, as piston 24 moves downward within liner 18, aposition will eventually be reached at which air intake ports 32 are nolonger blocked by piston 24 and instead are fluidly communicated withcombustion chamber 22. When air intake ports 32 are in fluidcommunication with combustion chamber 22 and a pressure of air at airintake ports 32 is greater than a pressure within combustion chamber 22,air will pass through air intake ports 32 into combustion chamber 22. Itis contemplated that gaseous fuel (e.g. methane or natural gas), may beintroduced into combustion chamber 22 (e.g. radially injected) throughat least one of air intake ports 32. The gaseous fuel may mix with theair to form a fuel/air mixture within combustion chamber 22.

Eventually, piston 24 will start an upward movement that blocks airintake ports 32 and compresses the air/fuel mixture. As the air/fuelmixture within combustion chamber 22 is compressed, a temperature of themixture may increase. At a point when piston 24 is near TDC, a liquidfuel (e.g. diesel or other petroleum-based liquid fuel) may be injectedinto combustion chamber 22 via a liquid fuel injector 36. The liquidfuel may be ignited by the hot air/fuel mixture, causing combustion ofboth types of fuel and resulting in a release of chemical energy in theform of temperature and pressure spikes within combustion chamber 22.During a first phase of the power/exhaust/intake stroke, the pressurespike within combustion chamber 22 may force piston 24 downward, therebyimparting mechanical power to crankshaft 30. At a particular pointduring this downward travel, one or more gas exchange ports (e.g.,exhaust ports) 34 located within cylinder head 20 may open to allowpressurized exhaust within combustion chamber 22 to exit and the cyclewill restart.

Liquid fuel injector 36 may be positioned inside cylinder head 20 andconfigured to inject liquid fuel into a top of combustion chamber 22 byreleasing fuel axially towards an interior of cylinder liner 18 in agenerally cone-shaped pattern. Liquid fuel injector 36 may be configuredto cyclically inject a fixed amount of liquid fuel, for example,depending on a current engine speed and/or load. In one embodiment,engine 10 may be arranged to run on liquid fuel injections alone or asmaller amount of liquid fuel mixed with the gaseous fuel. The gaseousfuel may be injected through air intake port 32 into combustion chamber22 via any number of gaseous fuel injectors 38. The gaseous fuel may beinjected radially into combustion chamber 22 through a corresponding airintake port 32 after the air intake port 32 is opened by movement ofpiston 24.

Engine 10, utilizing fuel system 14, may consume two types of fuels whenit is run as a dual-fuel engine. It is contemplated that the gaseousfuel may produce between 40% and 85% of a total energy output of engine10. For example, the gaseous fuel may produce between 60% and 65% of thetotal energy output, with the liquid fuel producing the remaining 35% to40%. In any case, the liquid fuel can act as an ignition source suchthat a smaller amount will be necessary than what is needed for engine10 if it were running on only liquid fuel.

As shown in FIG. 1, gaseous fuel injector 38 may be positioned adjacenta wall 42 of engine block 12, such that a nozzle 54 of injector 38 is indirect communication with one of air intake ports 32 of an adjacentengine cylinder 16. Gaseous fuel injector 38 may be connected at anopposing external end to power and control components (not shown) offuel system 14. These components may include, among other things, wiringto supply electrical power, a means to convert the electrical power intomechanical power (e.g. a solenoid), a controller configured to providesignals to the solenoid, and/or a regulator that at least partiallycontrols a flow rate and/or pressure of fuel into cylinder 16. A supplyline 52 may be positioned inside an air box 40 and connected betweengaseous fuel injector 38 and a fuel source (not shown) at a distal end.It is contemplated that supply line 52 may supply gaseous fuel tomultiple gaseous fuel injectors 38, if desired. That is, supply line 52may function as a manifold that extends along a length of air box 40 andengine 10.

High temperatures inside engine 10 may be created by fuel combustioninside cylinder 16 and through frictional heat produced by rapidlymoving parts, such as piston 24. The heat may emanate to nearby parts ofengine 10, causing their temperature to rise. One of these parts mayinclude gaseous fuel injector 38.

Cooling may be required to maintain gaseous fuel injector 38 at workingtemperatures that improve efficiency and to achieve a desirable partlifetime. Temperatures may be lowered by supplying a coolant to absorbsome of the heat from gaseous fuel injector 38 and its surroundingsand/or by supplying a lubricant to reduce friction within gaseous fuelinjector 38. In the disclosed embodiments, gaseous fuel injector 38 mayneed to be in a surrounding temperature of approximately 170 to 180° F.in order to operate properly. That is, air box 40, in which gaseous fuelinjector 38 is situated, may need to be cooled to less than about 170 to180° F. For this purpose, a primary cooling line 66 may run inside airbox 40 to supply a coolant to various parts of engine 10 and/or tomaintain the temperature inside air box 40 at the desired level. Primarycooling line 66 may be a dedicated coolant supply line that supplies acoolant to various parts of engine 10 or, alternatively, primary coolingline 66 may represent an oil supply line that supplies oil to thecomponents of engine 10 and also cools air box 40.

An additional cooling scheme may be necessary to further cool gaseousfuel injector 38 and its constituent parts, since gaseous fuel injector38 may be directly adjacent cylinder 16. Specifically, it may bepossible for gaseous fuel injector 38 to reach temperatures as high as210° F., even when air box 40 is cooled to below 170-180° F. Above thesetemperatures, any electrical components of gaseous fuel injector 38 maywork inefficiently or fail completely.

The coolant supplied by primary cooling line 66 may be utilized to coolgaseous fuel injector 38 in the same manner it cools other parts ofengine 10. In particular, an auxiliary cooling line 70 may be routedfrom primary cooling line 66 to individual gaseous fuel injectors 38 tocool the components of gaseous fuel injectors 38 via conductive heattransfer. Various arrangements for routing auxiliary cooling line 70 maybe possible.

As depicted in FIG. 1, auxiliary cooling line 70 may be configured todirect coolant into or near gaseous fuel injector 38. For example,coolant in auxiliary cooling line 70 may directly cool gaseous fuelinjector 38 by routing coolant into a valve block 53 housing componentsof gaseous fuel injector 38 and/or by directing coolant through or overnozzle 54 of gaseous fuel injector 38. Alternatively, coolant mayindirectly cool gaseous fuel injector 38 by allowing coolant to flowthrough a cooling jacket (not shown) that surrounds one or morecomponents of gaseous fuel injector 38 that need to be cooled. Thecoolant, after passing through or around gaseous fuel injector 38, maybe directed back to engine block 12 via return passage 68.

FIG. 2 depicts an alternative embodiment, in which cooling may beachieved by fuel that is subsequently injected into cylinder 16 bygaseous fuel injector 38. That is, instead of recirculating the coolantfrom gaseous fuel injector 38 back into engine 10, the coolant (beingliquefied natural gas) may instead be directed via a fuel cooling line72 into gaseous fuel injector 38 for injection. Specifically, fuel,after passing through and cooling gaseous fuel injector 38, may bedirected through fuel cooling line 72 into an injection conduit 74 ofgaseous fuel injector 38.

Liquefied Natural Gas (LNG) may need to be stored at a low temperatureof about −165° C., which works well in the cooling process describedabove. In addition, the LNG must change states before being injected bygaseous fuel injector 38 as a gaseous fuel. This state change mayrequire the temperature of the LNG to be raised above about −160° C. Inthe disclosed embodiment the LNG, as it passes through and/or aroundvalve block 53 of gaseous fuel injector 38, may reach the elevatedtemperature required for gasification, just prior to entering theinjection conduit 74 of gaseous fuel injector 38 for injection intocombustion chamber 22.

INDUSTRIAL APPLICABILITY

Fuel system 14 may be used in conjunction with any gaseous fueled ordual-fuel engine. Fuel system 14 may be a substitute for a liquid-onlysystem in order to utilize the associated engine in a cleaner and morecost-efficient manner. Either application may utilize one of theexemplary disclosed cooling arrangements to provide the necessarycooling of gaseous fuel injector 38.

In use, fuel system 14 may supply liquid fuel and/or gaseous fuel tocombustion chamber 22 of cylinder 16. Combustion of the fuel insidecylinder 16 may cause pressure and temperature spikes. Surroundingengine parts (e.g. gaseous fuel injector 38) may increase in temperaturedue to this process. The cooling arrangements depicted in FIGS. 1-2 maybe utilized to cool gaseous fuel injector 38.

As described above, the cooling arrangement of FIG. 1 may utilize adedicated coolant or an engine lubrication oil to cool gaseous fuelinjector 38. This may be possible because the coolant and/or oil maytypically be supplied at a temperature below a working temperature ofgaseous fuel injector 38. The lower temperature coolant or oil may onlyneed to be directed through air box 40 to the components of gaseous fuelinjector 38. For example, the coolant and/or oil may need to passthrough or around valve block 53 and/or nozzle 54 of gaseous fuelinjector 38. The close proximity of the lower temperature coolant and/oroil may absorb heat through conductive heat transfer from the highertemperature components of gaseous fuel injector 38. This heat transfermay help to maintain gaseous fuel injector 38 below threshold levelsthat help preserve the efficiency and integrity of its components.

As depicted in FIG. 2, the fuel injected by gaseous fuel injector 38 mayfirst be brought to gaseous fuel injector 38 by strategically routingthe fuel from supply line 52 through and/or around valve block 53 andnozzle 54. As the LNG passes through or around valve block 53 and nozzle54, heat emanating from gaseous fuel injector 38 may be absorbed by thefuel and used to gasify the fuel prior to injection.

The use of coolant in auxiliary cooling line 70 may be particularlypractical when the engine is in a single-fuel mode because gaseous fuelinjector 38 may not be in use to inject gaseous fuel, but a need forcooling would remain.

The use of LNG to cool gaseous fuel injector 38 may be beneficial toreduce the number of parts required to allow fuel system 14 to operate.In particular, components normally used to gasify the LNG may be reducedor omitted by using cooling components to accomplish both cooling andgasification operations. This may be especially advantageous if fuelsystem 14 is utilized in a retrofit application.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed engine andfuel system. Other embodiments will be apparent to those skilled in theart from consideration of the specification and practice of thedisclosed fuel system. It is intended that the specification andexamples be considered as exemplary only, with a true scope beingindicated by the following claims and their equivalents.

What is claimed is:
 1. A fuel system for an engine, comprising: agaseous fuel injector configured to inject gaseous fuel radially into acylinder of the engine; a primary cooling line configured to circulate acoolant through the engine; and an auxiliary cooling line fluidlyconnecting the primary cooling line with the gaseous fuel injector. 2.The fuel system of claim 1, further including an air box housing thegaseous fuel injector, the primary cooling line, and the auxiliarycooling line.
 3. The fuel system of claim 2, wherein the air box isconfigured to direct air through an air intake port of the cylinder. 4.The fuel system of claim 3, wherein the gaseous fuel injector is mountedat the air intake port to inject gaseous fuel with the incoming air. 5.The fuel system of claim 1, wherein the auxiliary cooling line directscoolant around a valve block of the gaseous fuel injector.
 6. The fuelsystem of claim 1, wherein the auxiliary cooling line directs coolantthrough a valve block of the gaseous fuel injector.
 7. The fuel systemof claim 1, further including a liquid fuel injector configured toinject liquid fuel into the cylinder.
 8. The fuel system of claim 1,further including a return line fluidly connecting the auxiliary coolingline to the primary cooling line.
 9. The fuel system of claim 1, whereinthe coolant is water.
 10. The fuel system of claim 1, wherein thecoolant is oil.
 11. The fuel system of claim 1, wherein the coolant isfuel to be injected by the gaseous fuel injector.
 12. A method ofcooling a fuel injector of an engine comprising: circulating a coolantvia a primary cooling line located in an air box of the engine;directing the coolant through an auxiliary cooling line to a gaseousfuel injector to cool the gaseous fuel injector; and returning thecoolant to the engine.
 13. The method of claim 12, further includingdirecting air from the air box of the engine through an air intake portin a cylinder of the engine.
 14. The method of claim 13, furtherincluding injecting gaseous fuel from the gaseous fuel injector throughthe air intake port with the incoming air.
 15. The method of claim 12,wherein directing the coolant to a gaseous fuel injector includesdirecting the coolant around a valve block of the gaseous fuel injector.16. The method of claim 12, wherein directing the coolant to a gaseousfuel injector includes directing the coolant through a valve block ofthe gaseous fuel injector.
 17. The method of claim 12, wherein thecoolant is water.
 18. The method of claim 12, wherein the coolant isoil.
 19. The method of claim 12, wherein the coolant is fuel to beinjected by the gaseous fuel injector.
 20. An engine comprising: anengine block defining a cylinder; a piston; a combustion chamber atleast partially defined by the cylinder and the piston; a plurality ofair intake ports defined by the cylinder; a gaseous fuel injectorconfigured to inject gaseous fuel radially through one of the pluralityof air intake ports and into a cylinder of the engine; an air boxconfigured to direct air through the plurality of air intake ports andinto the cylinder; a primary cooling line located in the air boxconfigured to circulate a coolant through the engine; and an auxiliarycooling line fluidly connecting the primary cooling line with thegaseous fuel injector.